I just checked, and almost all great dane webpages will tell you the same..

...Feeding Great Danes puppy food, even large breed formulas can have serious consequences. The protein and fat levels of most brand puppy foods are way too high for a growing Dane.
...It is crucial to "grow them slow", slow steady growth is key to proper development!...
http://www.all-about-great-danes.com...eat-danes.html

..Remember, slow, steady growth will do more for your puppy than rapid growth that can happen with puppy foods. The puppy will eventually reach its genetic potential, but without the additional risk to bone that comes from high proteins and supplementation (calcium/minerals) or puppy foods.
..Do not feed puppy foods, even those developed for giant breeds.
http://www.daneangelnetwork.org/puppyfood.htm

...Dane puppies should not be fed puppy food. The high calories and protein levels of puppy food encourage rapid growth spurts, which is linked to growth related problems (i.e. Pano, HOD) in giant breeds.
http://www.fotodanes.com/kibble.htm

And for dobermans too....

..They also discontinue feeding puppy food at an early age, ~4 months. This practice is thought to help reduce the incidence of Panosteitis (wandering lameness) and reduce the rapid growth produced by a higher ratio of protein found in most commercial puppy foods.
http://www.puppypetsupplies.net/tag/doberman-puppy/